Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Tow hitch (optional extra)
The trailer module (TRM) (4/110) ensures that the correct type of signals are transmitted to the tow hitch cable harness.
The rear electronic module (REM) (4/58) receives messages on the controller area network (CAN) from the central electronic module (CEM) (4/56) about when output signals to the turn signal lamps, parking lamps, back-up lamps and fog lamps should be activated. The rear electronic module (REM) then transmits a direct signal to the trailer module (TRM).
The trailer module (TRM) forwards the signal to the tow hitch cable harness.
The +12 V output signal is activated when the ignition key is turned from position 0 to I, II or III. The rear electronic module (REM) transmits the signal.
+12 V supply is direct from the battery.
The rear electronic module (REM) transmits messages on the controller area network (CAN) to the central electronic module (CEM) and driver information module (DIM) (5/1), if a trailer is connected to the tow hitch connector socket. A separate indicator lamp in the driver information module (DIM) indicates when the turn signal lamps are used and the trailer is connected. If one of the turn signal lamp bulbs is defective the separate indicator lamp will not light.
The output signals for back-up lamps, fog lamps and +12 V in the socket for the tow hitch connector are market dependent. The socket for the tow hitch connector is available in a number of variants with different numbers of pins.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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